Couple with child in the car ram police vehicle after armed robbery in NSW

A man and woman are on the run after robbing a NSW service station and ramming a police car with their four-wheel-drive while carrying a young girl.

Police said the couple filled up their Jeep Cheerokee at a petrol station on the Stuart Highway at Balranald in the state's southwest between 5.15 and 5.30pm (AEDT) yesterday afternoon before driving off without paying.

They then went to a supermarket on Market Street where they threatened staff with a large knife before fleeing with cash.

Highway Patrol officers spotted the Jeep, which had stolen number plates, on the Stuart Highway near Euston and tried to stop it before a pursuit was initiated.

Police said during the chase the Jeep stopped before reversing into the front of the highway patrol car and ramming it, causing extensive damage.

The Jeep then took off again and was found abandoned a short distance away.

Police believe the couple and child may have been picked up by interstate truck drivers and are asking anyone with information on their movements to contact Crime Stoppers on 1800 333 000.